Rule description contains only rule classes. Split documentation between repositories first step

[jfdenise]

• Clean up rule descriptions. Used to contain a mix of rule instances and types. Only types of rules are documented.
• The doc plugin will be used to generate the feature-packs and layers from the wildfly-galleon-feature-packs repo. Doing so it is in sync when upgrading/adding feature-packs. The glow documentation will only reference this documentation.